1. Field of the Invention
The present invention relates to a semiconductor device testing apparatus (commonly known as IC tester) for testing various types of semiconductor devices including semiconductor integrated circuits (commonly called IC), and more particularly to a semiconductor device transporting and handling apparatus (commonly known as handler), connected to the testing apparatus, for transporting various types of semiconductor devices to a test section to test them, and carrying the tested semiconductor devices out of the test section for transport to a desired location.
2. Description of the Related Art
As is well known, many of semiconductor device testing apparatus for testing various types of semiconductor devices including ICs have a semiconductor device transporting and handling apparatus (which will be referred to as handler hereinbelow) connected thereto for transporting semiconductor devices to be tested, i.e. devices under test (commonly called DUT) to the test section to be brought into electrical and mechanical contact with device-testing sockets, and after testing, carrying the tested semiconductor devices out of the test section for transport to a predetermined location. For simplicity of description, the semiconductor device testing apparatus will be described in the following disclosure by taking ICs which are typical of semiconductor devices by example.
First, one example of the semiconductor device testing apparatus of the type to which the present invention is intended to be applied will be described with reference to FIGS. 5 and 6.
FIG. 5 is a plan view illustrating the general construction of one example of the conventional semiconductor device testing apparatus (which will be referred to as IC tester hereinafter), particularly showing the general construction of the handler. This handler comprises a generally rectangular base plate 10, and first and second X-Y transport units 20 and 30 which are capable of transporting articles in both the X- and Y-axis directions, the first and second X-Y transport units 20 and 30 being disposed on the base plate 10 in longitudinally (in the right to left direction as viewed in the drawing) opposed relation to each other. The longitudinal direction is referred to as X-axis direction herein.
The first X-Y transport unit 20 includes a pair of first parallel X-axis rails 21A, 21B extending for a predetermined length in the X-axis direction over and along the opposite major lateral sides of the base plate 10 from adjacent the left end thereof as viewed in the drawing, a first movable arm 26 spanning the X-axis rails 21A, 21B orthogonally therewith and movably mounted on the rails in the X-axis direction therealong, and a first X-Y carriage 24 mounted on the movable arm 26 for movement therealong in the Y-axis direction.
The second X-Y transport unit 30 includes a pair of second parallel X-axis rails 31A, 31B extending for a predetermined length in the X-axis direction over and along the opposite major lateral sides of the base plate 10 from adjacent the left end thereof as viewed in the drawing, a second movable arm 36 spanning the X-axis rails 31A, 31B orthogonally therewith and movably mounted on the rails in the X direction therealong, and a second X-Y carriage (not shown) mounted on the movable arm 36 for movement therealong in the Y direction.
It will thus be understood that the first X-Y carriage 24 is movable by the first X-Y transport unit 20 constructed as described above to any desired point within the generally rectangular area (A) defined between the pair of first X-axis rails 21A, 21B as shown in dotted lines while the second X-Y carriage is likewise movable by the second X-Y transport unit 30 to any desired point within the generally rectangular area (B) defined between the pair of second X-axis rails 31A, 31B as shown in dotted lines. That is, the area (A) is the region within which the first X-Y transport unit 20 is capable of transporting articles while the area (B) is the transportable region of the second X-Y transport unit 30.
Disposed in the lower portion of the area (A) successively from the right side to the left side as viewed in the drawing are an empty tray storage section 46 for accommodating empty trays stacked one on another, a supply tray 41 loaded with ICs to be tested (ICs under test), two of the sorting trays 42 and 43 for sorting and storing tested ICs on the basis of the test results. The remaining two sorting trays 44 and 45, and a planar heater plate 50 for heating ICs under test to a predetermined temperature are disposed successively from the left to right side in the upper portion of the area (A) as viewed in the drawing. It is needless to say that the arrangement of the trays 41-45, the empty tray storage section 46 and the heater plate 50 and the number of the sorting trays 42-45 are illustrated herein as only one example and that they may be varied as required.
Disposed within the area (B) is the test section TS of the IC tester within which there are mounted IC sockets, although not shown, with which ICs under test are to be put into electrical contact. As the illustrated handler is configured to test two ICs under test at one time, the test section TS is equipped with two sockets.
The illustrated handler is further provided with first and second buffer stages BF1 and BF2, respectively which are reciprocally movable in the X-axis direction between a predetermined position in the area (A) and a predetermined position in the area (B). More specifically, the first buffer stage BF1 is reciprocally movable in the X-axis direction between that section within the area (A) adjacent the right hand side of the heater plate 50 and a predetermined position in the area (B) while the second buffer stages BF2 is reciprocally movable in the X-axis direction between that section within the area (A) adjacent the right hand side of the empty tray storage section 46.
The first buffer stage BF1 performs the function of transferring ICs under test heated to a predetermined temperature from the area (A) to the area (B) while the second buffer stage BF2 acts to carry the tested ICs from the area (B) to the area (A). It is to be understood that the provision of these buffer stages BF1 and BF2 permits the first and second X-Y transport units 20 and 30 to accomplish their transport operations with no interference with each other.
The first X-Y transport unit 20 described above is configured to convey ICs under test to the heater plate 50 for applying a predetermined thermal stress to the ICS, and then perform the operation of transferring the ICs under test heated to a predetermined temperature onto the first buffer stage BF1 and the operation of transferring the tested ICs from the second buffer stage BF2 onto the predetermined sorting trays which tested ICs have been transported from the area (B) to the area (A) by the second buffer stage BF2.
On the other hand, the second X-Y transport unit 30 is configured to perform the operation of transporting ICs under test as conveyed by the first buffer stage BF1 into the area (B) to the test section TS and the operation of transferring the tested ICs from the test section TS onto the second buffer stage BF2.
The heater plate 50 described above may be formed of plate-like metal stock for example, and is provided with a plurality of IC receiving recesses or pockets 51 for accommodating ICs under test. ICs to be tested are transported from the supply tray 41 into these IC receiving recesses 51 by the first X-Y transport unit 20. These IC receiving recesses 51 are typically arrayed in the form of a matrix composed of a plurality of rows and a plurality of columns. The heater plate 50 is maintained in an elevated temperature somewhat higher than the temperature to which ICs to be tested are to be applied. The ICs to be tested are thus heated to a predetermined temperature before being transported by means of the first buffer stage BF1 to the test section TS. The first and second X-Y transport units 20 and 30 are each provided with their own Z-axis drive units which perform the operation of picking up ICs out of the trays, the heater plate 50 or the test section TS (sockets) and the operation of dropping off ICs onto the trays, the heater plate 50 or the test section TS.
FIG. 6 illustrates the general construction of one example of the Z-axis drive unit 60 mounted on the first X-Y transport unit 20. As illustrated, the movable arm 26 extending in the Y-axis direction of the first X-Y transport unit 20 comprises a hollow member having a generally C-shaped cross-section, in the hollow interior of which a threaded shaft 22 and a guide shaft 23 likewise extending in the Y-axis direction are housed. Specifically, the threaded shaft 22 and guide shaft 23 extend in the Y-axis direction through the body portion of the first X-Y carriage 24 which is formed with threads engageable with the threads of the threaded shaft 22. The guide shaft 23 has no threads thereon so as to permit sliding movement of the body portion of the first X-Y carriage 24 relative to the guide shaft 23 which in turn acts to stabilize the movement of the X-Y carriage 24 in the Y-axis direction.
With the construction as described above, driven rotation of the threaded shaft 22 will move the first X-Y carriage 24 in the Y-axis direction in a stable manner. It is to be noted that the movement of the X-Y carriage 24 in the X-axis direction is effected by the movement of the movable arm 26 in the X-axis direction.
Extending horizontally (in the X-axis direction as viewed in FIG. 5) from the too of the body portion of the first X-Y carriage 24 is an arm 24A on the underside of which are vertically and downwardly mounted a plurality of (four in this example) first, second, third and fourth air cylinders S1, S2, S3 and S4, respectively, as shown in FIG. 5. In FIG. 6, the second air cylinder S2 is invisible as it is hidden behind the first air cylinder S1. Likewise, the fourth air cylinder S4 is invisible as it is hidden behind the third air cylinder S3. Each of the movable rods of the air cylinders S1, S2, S3 and S4 has a vacuum pick-up head mounted on its lower end.
While in the illustrated example the Z-axis drive unit 60 is adapted to actuate the first and second air cylinders S1 and S2 in a pair and the third and fourth air cylinders S3 and S4 in a pair so as to vacuum attract two ICs at a time thereagainst for transport, this is only an example.
One set of the first and second air cylinders S1 and S2 are employed to transport ICs under test heated to a predetermined temperature in the heater plate 50 to the first buffer stage BF1. In view of this, the vacuum pick-up heads 61 (shown as having ICs under test attracted thereagainst) mounted on the first and second air cylinders S1 and S2 are equipped with heaters (not shown) for maintaining the temperature of the heated ICs under test. The vacuum pick-up heads 62 mounted on the other set of the third and fourth air cylinders S3 and S4 are equipped with no heaters, because they are used to transport ICs at their normal temperature. Specifically, the vacuum pick-up heads 62 are used when transporting ICs from the supply tray 41 to the heater plate 50 and the tested ICs from the second buffer stage BF2 to corresponding one of the sorting trays 42, 43, 44 and 45.
The second carriage, not shown, mounted on the movable arm 36 of the second X-Y transport unit 30 is also provided with a Z-axis drive unit similar in construction to the Z-axis drive unit 60. However, since the second X-Y transport unit 30 is positioned in a mirror-image relation with the first X-Y transport unit 20, the movable arm 36 has a configuration symmetrical with respect to that of the movable arm 26 as shown in FIG. 6 (the movable arm 26 is open on its right-hand side whereas the movable arm 36 is open on its left-hand side), and four air cylinders are mounted on the left side of the movable arm 36. It should be noted that in the second carriage as well, the Z-axis drive unit is adapted to actuate the first and second air cylinders in a pair and the third and fourth air cylinders in a pair so as to vacuum attract two ICs at a time thereagainst for transport. One set of the air cylinders are employed when transporting ICs under test heated to a predetermined temperature from the first buffer stage BF1 to the test section TS. In view of this, the vacuum pick-up heads mounted on these cylinders are equipped with heaters for maintaining the temperature of the heated ICs under test. The vacuum pick-up heads 62 mounted on the other set of air cylinders are equipped with no heaters and are used when transporting ICs at their normal temperature, that is, from the test section TS to the second buffer stage BF1. It will be apparent to those skilled in the art the construction of the Z-axis drive unit may be modified in various ways.
As discussed above, this type of IC tester is configured to heat ICs to be tested to a predetermined temperature in the heater plate 50 and test the ICs while maintained at that predetermined temperature. There is a considerably high demand for the IC tester of the type utilizing a simplified type of heater means such as the heater plate 50 as described above, because of the high initial cost of the IC tester of the type utilizing a constant temperature chamber capable of maintaining ICs under test heated at a predetermined temperature and employing the test section TS enclosed in the constant temperature chamber to effect the testing.
It should be here pointed out that in case the package of an IC to be tested is of a configuration having terminal pins from its four sides or opposed two sides as is the case with the surface-mounted type QFP (Quad Flat Package) or SOP (Small Outline Package) for example, the IC receiving recess 51 in the heater plate 50 may have a bottom 52 raised by a predetermined height as shown in FIG. 7 so as to provide a surface contact between the bottom 52 of the recess 51 and the bottom of the IC package PK and hence a sufficiently large area of contact between the IC package PK and the heater plate 50 in the IC receiving recess 51 to permit the IC to be heated to a desired temperature approximating to the temperature of the heater plate 50.
In contrast, the package of area array IC such as the BGA (Ball Grid Array) package and the CSP (Chip Size Package) has terminals (electrodes) formed over approximately the entire surface area of the mounting side (the bottom surface of the package), so that it is impossible to place that portion of the undersurface of the IC package PK formed with terminals T in direct contact with the bottom surface of the IC receiving recess 51 in the heater plate 50, as seen in FIG. 8. For this reason, the bottom surface of the IC receiving recess 51 is formed with a stepped ledge 53 for supporting the outer margin of that portion of the undersurface of the IC package PK formed with terminals T so as to lift the terminals T off the bottom of the IC receiving recess 51.
However, if the IC receiving recesses 51 were constructed with such stepped ledges 53, the surface areas of contact between the IC packages PK and the heater plate 50 in the IC receiving recesses 51 would be undesirably reduced, resulting in failure to heat the ICs to a desired temperature.
More specifically, while in this type of IC tester it is a common practice to heat ICs under test to 125.degree. C. or over for example, the ultimate temperature that the ICs under test could reach with the IC receiving recesses 51 as constructed as shown in FIG. 8 was limited to around 115.degree. C. if the heater plate 50 had a surface temperature of 130.degree. C., but it was not possible to raise the temperature of the ICs to be tested beyond 125.degree. C.
In view of this while it was proposed to set the surface temperature of the heater plate 50 at a higher level, to that end it required that those parts of the handler to be contacted with the heater plate 50 and the vacuum pick-up heads equipped with heaters have an increased heat resistance, leading undesirably to an increase in the cost of manufacture. In addition, the program for controlling the temperature of the heater plate 50 need be modified, requiring cumbersome operations and time.